Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
  • B21D22/26—Deep-drawing for making peculiarly, e.g. irregularly, shaped articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D37/00—Tools as parts of machines covered by this subclass
  • B21D37/16—Heating or cooling

Definitions

• the present disclosure relates to a heat treatment method of blank sheets of aluminum alloys, and especially to a method suitable for blank sheets of any aluminum alloy grade, composition or temper.
• the hot forming of blank sheets is important, in particular hot forming of blank sheets of high strength aluminum alloys.
• the aluminum alloy grade material compositions and tempers may vary from different material suppliers.
• the resulting formed components using the known methods are very sensitive to different compositions and tempers.
• a method of forming a 6xxx or 7xxx series Al alloy blank into a component comprises the steps of heating the blank to a solutionization (SHT) temperature, TSHT, for the alloy of the blank at a heating station and keeping the blank at said SHT temperature until SHT is complete, cooling the blank at a cooling station to an intermediate temperature, TITM, at which the kinetic movement for the alloy in the blank stops and at a cooling rate that is high enough such that re-crystallization in the alloy of the blank does not occur, forming the blank in a forming tool, quenching the formed blank to room temperature, TE, and artificially ageing the formed and quenched blank in an ageing station.
• SHT solutionization
• a method is provided that, with high accuracy of the formed components and low amount of springbacks, is suitable for any 6xxx or 7xxx series aluminum alloy grade sheet blank.
• the time in which the blank is kept at or above the solution heat treatment (SHT) temperature may be chosen to be sufficient to ensure maximum concentration of hardening elements, such as copper, zinc, magnesium, manganese, silicon etc. in the solid solution.
• the concentration and rate of dissolution of these elements in the solid solution may increase with increasing temperature.
• the SHT composition of the solid solution may be preserved at the intermediate temperature. If the blank were to be cooled in a too slow rate, the alloying elements may diffuse through the solid solution and concentrate at the grain boundaries, in large voids, undissolved particles or other undesired locations. To achieve improved strength properties of the formed part, it may be desirable to avoid such recrystallization and decrease the diffusion process and maintain the alloying elements in the solid solution by providing a rapid cooling.
• the cooling rate to achieve this may be selected depending on the aluminum alloy grade and composition of the blank. Further, a quenching rate may be selected depending on the aluminum alloy grade and composition of the blank.
• the intermediate temperature may be a temperature in an intermediate temperature range being above room temperature and below the SHT temperature.
• the time required for a given amount of precipitation may increase due to low solute diffusion coefficients.
• the rate of precipitate formation is low due to the inability of atoms to diffuse, increased nucleation or precipitation and growth at the temperature range.
• an intermediate temperature for a 7xxx series Al alloy blank may be chosen between 400-420 °C. Further, for a AA6082 Al alloy blank, the intermediate temperature may be chosen as 300-350 °C. At such temperatures, the kinetic movement in the alloy material of the blank may have stopped.
• the cooling to the intermediate temperature may be performed at a cooling station being separate from the forming tool.
• the cooling may thereby be provided fast and with homogeneous temperature in the blank.
• a cooling rate of at least 30 K/s may be chosen.
• a cooling rate of at least 30 K/s, at least 50 K/s, or preferably about 100 K/s may be chosen.
• the intermediate temperature may be selected depending on the Al alloy of the blank, and being above 100 °C.
• the intermediate temperature should be selected as a temperature wherein the kinetic movement of the alloy material of the blank stops.
• the optimal intermediate temperature may differ.
• the intermediate temperature may be above 100 °C.
• the intermediate temperature may be selected being the highest possible temperature at which the kinetic movement in the present alloy material stops.
• the forming tool may be preheated to the intermediate temperature.
• the blank may thereby be formed at the
• the temperature of the blank may thereby be controlled during the forming, which may improve the accuracy in the properties of the final formed component.
• the blank may be kept at the intermediate temperature during the forming step in the forming tool.
• the temperature of the tool may be controlled in order to keep the temperature of both the tool and the blank stable at the intermediate temperature during the forming.
• the temperature of the forming tool may be controlled in order to quench the formed blank to room temperature.
• a temperature control function may be provided for the forming tool in order to control the temperature of the forming tool to the intermediate temperature throughout the forming step.
• the forming and the quenching may be performed in separate forming tools.
• a first forming tool may form the blank at the intermediate temperature, and a second forming tool may quench the blank to room temperature.
• the first forming tool may be preheated to the intermediate temperature, thereby keeping the blank at the intermediate temperature during the forming. The blank may then be transferred to the second forming tool, quenching the blank to room
• the second forming tool may be a cold forming tool.
• the first forming tool may not be preheated, thereby cooling the blank during the forming.
• the blank may then in the second forming tool be quenched in a controlled manner to room temperature in the second forming tool.
• a 6xxx or 7xxx series Al alloy blank forming system comprising a heating station configured to heat a blank to its SHT temperature, TSHT, a cooling station configured to cool the blank to an intermediate temperature TITM, at which the kinetic movement for the alloy in the blank has stopped and at a cooling rate that is high enough such that re-crystallization in the alloy of the blank does not occur, a forming tool configured to form and quench the blank, and an ageing station configured to provide an artificial ageing process to the formed and quenched blank.
• a heating station being configured to heat a blank to its SHT temperature it may be meant a heating station comprising means capable of heating a blank inserted into the heating station to its SHT temperature.
• a cooling station configured to cool the blank to an intermediate temperature at which kinetic movement for the alloy in the blank has stopped and at a cooling rate that is high enough such that re-crystallization in the alloy of the blank does not occur it may be meant a cooling station comprising means capable of cooling a blank in the specified way.
• a forming tool configured to form and quench a blank it may be meant a forming tool comprising means capable of forming and quenching the blank.
• an ageing station configured to provide an artificial ageing process to the formed and quenched blank it may be meant an ageing station comprising means capable of such artificial ageing process.
• the heating station, the cooling station, the forming tool and/or the ageing station may further comprise means capable of providing additional functions as discussed above for the method.
• FIG. 1 shows a flow chart of a method according to an embodiment of the invention
• Fig. 2 shows a block scheme of a system according to an embodiment of the invention
• Fig. 3 shows a diagram view of a process of the method according to an embodiment of the invention
• Fig. 4 shows a flow chart of a method according to an embodiment of the invention
• Fig. 5 shows a block scheme of a system according to an embodiment of the invention.
• Fig. 6 shows a diagram view of a process of the method according to an embodiment of the invention.
• a method 100 comprises a first step of heating 102 a 6xxx or 7xxx series Al alloy blank 2 to the solutionization (SHT) temperature for the specific alloy of the blank 2.
• SHT solutionization
• a blank forming system 1 is provided, wherein the heating 102 is performed in a heating station 10.
• the temperature of the blank 2 is kept at the SHT temperature or above until the solutionization of the alloy of the blank 2 is complete.
• the blank 2 is cooled 104 to an intermediate
• the cooling 104 is performed at a cooling station 20.
• the intermediate temperature is selected for the alloy of the blank 2 at which temperature the kinetic movement for the alloy stops.
• the cooling 104 is performed at a cooling rate high enough such that re- crystallization in the alloy of the blank 2 does not occur.
• the blank 2 is formed 106 in a forming tool 32 at a press station 30 in the blank forming system 1 .
• the press station 30 may be a press suitable for aluminum alloy blank sheet forming, such as a hydraulic press, a servo press (servo hydraulic or servo mechanical).
• the formed blank 2', or formed component 2' is quenched 108 in the forming tool 32 to room temperature.
• the formed blank 2' is artificially aged 1 10 at an ageing station 40.
• the ageing process is provided to control and limit the recrystallization in the alloy material of the blank 2.
• Fig. 3 illustrates the blank forming method 100 according to an embodiment of the present invention.
• the blank 2 is heated from room temperature TE to the SHT temperature TSHT, and kept at the TSHT for a necessary time ti -t2 as discussed above.
• the blank 2 is rapidly cooled to the intermediate temperature TITM at the necessary cooling rate as discussed above.
• the blank 2 is then formed during t2-h in the forming tool 32.
• the formed blank 2' is quenched to room temperature TE.
• the formed component 2' is processed for artificial ageing by being heated to an ageing temperature TA.
• the component 2' is kept at the ageing temperature TA during a period ts-t.6 until the ageing process is complete.
• the time t.3-t 4 provides a transfer of the formed blank to the ageing station 40.
• the blank 2 is transferred between the different stations 10, 20, 30, 40.
• the transfer may be performed such that minimal heat loss in the blank 2 is achieved.
• Figs. 4 and 5 illustrates a method 200 and system 3 according to an embodiment of the invention.
• the steps of heating 202 and cooling 204 correspond to the steps 102 and 104 as discussed above.
• the blank 2 is formed 206 in a preheated first forming tool 32a at a press station 30 in the blank forming system 3.
• the first forming tool 32a is preheated to the intermediate temperature.
• the blank 2 is thereby not further cooled when arranged in the first forming tool 32a.
• the intermediate temperature may be kept in the first forming tool 32a and the blank 2 throughout the forming process 106.
• the formed blank is moved to a separate cold second forming tool 32b.
• the blank is quenched to room temperature.
• the cold second forming tool 32b may further form and quench the blank to its final shaped component.
• Fig. 5 further illustrates an optional arrangement of ageing which can be used for either of the above presented embodiments.
• a first pre-ageing step is performed at a pre-ageing station 40a, in which the formed component 2' is heated to the ageing temperature TA, kept at TA until the pre-ageing is complete and then cooled to room
• the component 2' is again heated to TA, kept at TA for a time period and thereafter cooled to room temperature TE, to provide a paint baking of the component 2'.
• the component can be heated to a different temperature in the paint baking process than the temperature TA in the pre-ageing process.
• a two-step ageing process is thereby provided comprising pre-ageing and paint baking.
• the pre-ageing process is integrated in the
• the paint baking process may be performed at a later stage, whichever may be suitable for the production line.
• the use of the pre-ageing process prevents natural ageing after stamping in the second forming tool. Otherwise, natural ageing may occur after about 30 minutes for 7xxx series Al alloy materials or about one hour for 6xxx series Al alloy materials.
• the paint baking process cannot take effect on the formed component to achieve peak hardness.
• the pre-ageing process further enables post processing activities such as transport to another location, storage for a required period before assembly or joining operations. Then, the paint baking operation may be performed at the most suitable time to provide optimal peak hardness in a short cycle time and at a low cost. This may e.g. be after joining the formed component 2' to a desired assembly.
• Fig. 6 illustrates the process blank forming method 200 according to an embodiment of the present invention.
• the blank 2 is heated from room temperature TE to the SHT temperature TSHT, and kept at the TSHT for a necessary time ti-t2 as discussed above. Between .2 and t.3, the blank 2 is cooled to the intermediate temperature TITM at the necessary cooling rate as discussed above.
• the blank 2 is then formed during t.3-t 4 in the preheated first forming tool 32a. Between U and ts the formed blank 2' is quenched to room temperature TE in the second forming tool 32b.
• Fig. 6 further illustrate the process of the embodiment comprising a pre-ageing and a paint baking step as discussed above.
• the formed blank 2' is processed for artificial ageing by being heated to the ageing temperature TA and kept at the ageing temperature TA during a period t -te-
• the blank 2' is in the second ageing station 40b again heated to the ageing temperature TA and kept at TA between tn-ti2 until the ageing process is complete.
• the blank 2' formed to a final shaped component is then again cooled to room temperature T E .

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Heat Treatment Of Articles (AREA)
• Forging (AREA)

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• 2017
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• 2018
  • 2018-10-03 WO PCT/EP2018/076913 patent/WO2019068767A1/en active Application Filing
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  • 2018-10-03 US US16/652,908 patent/US20200299818A1/en not_active Abandoned
  • 2018-10-03 CN CN201880061712.0A patent/CN111315910A/zh active Pending
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